* May light synthetic quoted at $9.50/bbl above WTI
* Suncor oil sands turnaround expected shortly
* WCS for May $14.75/bbl under WTI, despite pipeline outage
CALGARY, Alberta, April 1 (Reuters) - Canadian light synthetic crude prices climbed to their highest levels in six months on Monday as Suncor Energy Inc prepared to take a major processing unit at its Alberta oil sands operation down for seven weeks of maintenance.
Heavy crude prices also maintained their recent strength despite the shutdown of Exxon Mobil Corp's 90,000 barrel a day Pegasus pipeline in the southern United States following a rupture late Friday.
Light synthetic for May delivery last sold for $9.50 a barrel over benchmark West Texas Intermediate crude, up $2.50 from Thursday, according to Shorcan Energy Brokers.
That was its highest since October 2.
Synthetic supplies in May will be constrained by the planned maintenance at the 100,000 barrel per day Upgrader 1 unit at Suncor's northern Alberta project site, which is expected to begin shortly. The overall oil sands plant normally produces up to 350,000 bpd.
Western Canada Select heavy blend for May was quoted at $14.75 a barrel under WTI, compared with a settlement of $14.50 a barrel on Thursday.
Part of the recent strength in Canadian heavies - WCS fetched $40 a barrel less than WTI in January - has been the slow start-up of the first phase of Imperial Oil Ltd's 110,000 Kearl oil sands project. That has kept previously anticipated volumes out of the market, industry sources said.
Imperial said in Monday it expects to start producing marketable diluted bitumen the C$12.9 billion ($12.69 billion) project in "the next few days."
Meanwhile, Exxon Mobil continued efforts to clean up thousands of barrels of heavy Canadian crude oil spilled from a the aging Pegasus pipeline in Arkansas. A company spokesman declined to speculate about when it would be fixed and restarted.
The line carries Canadian oil to the U.S. Gulf region from southern Illinois.